As a check valve, a technique disclosed in Patent Literature 1 below, for example, has been proposed. The check valve of Patent Literature 1 includes a valve body and a receiving member. The valve body includes a ring-shaped contact part on the outer side, and a projection at the center inside the ring-shaped contact part, and the ring-shaped contact part and the projection are coupled to each other by a coupling part.
A fluid path (hole) is formed at the center of the receiving member. The ring-shaped contact part of the valve body is a portion that closely contacts the outer circumferential portion of the receiving member. The projection of the valve body is configured to make line contact with the entire circumference of the ridge line on the edge of the fluid path.
The check valve of Patent Literature 1 aims to enhance the degree of sealing of the fluid path by configuring the projection of the valve body so as to make line contact with the entire circumference of the ridge line on the edge of the fluid path formed in the receiving member.